Method and means for estimating the phlegmatizing properties of waxes as applied to high explosives



fiatented Nov. 28, 1950 Ive-Drawing. Application:January'fifl'M'i; SeriarNo. 722,2181.

(Grantedunder' thee act of? March .3; 188-3} as amended April" 30, 1928;; 37.0:- G. 75.7.)

4 iGlaimS:

The" invention described herein may -b'e manu faotumdmnd"used byor-for the-Government fon governmental purposes without the payment to -usof any royalty thereon.

' Due to the insistent demand for explosivesofii "increased brisance there has come into use; in: recent years, a number of explosives whichwere" already known but which had been consideredtoo sensitive, i. e., too sensitive to shock and to friction to be of militar value. Their manu= facture, loading and transportation has beeruconsidered hazardous and much efiort has been'expended in finding ways to desensitize them in order to increase the safety factor in connection with their use. p g Experience has shown that these undesirable properties may be modified and largely elimi- *nated by coating the explosives with various inert materials such as waxes known by the following trade namesg- AmberwaxMPetroleum Wax melt ing-point 82 86 Bareeo (dil 'Goz'; manufae -turen).'=, Sant'owax (Hydrbcarbon wax; melting point, 83 C2; Monsanto l Chemical Col- Aristowax (Paraflinuwax; meltingmointfl-T-M Petroleum SpecialtyCm), Acrawax (Syntheticwvax; melting point: se -9 1m; Glyo'o Products Got), Albacen wax (Synthetic-wax;- meltirrg point 95437 C3; Glyco Hroduct's 60;); P'entawax 1-77 (85%pentaeryth rit-ol-ttetrastearate, 1'5 dipentaerythritol hexa stearate, melting pointi 70 73 (2, Heyden Brod ucte: Cox); Pentawax 286 (melting-point I=2O CI HeydemProduct's Cox); on natural resins suehras Karaya gum, gum elemi', gum:- copal, gum dam mar, or synthetic plastics such-as polystyrr-me; methyl? methacnylate; polyvinyl acetate: or conlnarone-indene', etc; Materialsof thisrtype' are generally: referred to as waxes "thnoughoutathis application;

' Inzthe search for: suitablepcoatingagents and: processes of I applicatione itzha's been-found neces sary tosinvestigate- -the properties of a large-num bee. of. agents. and application techniques. The latter is 4: important: because 1 various samples of explosives all 5 containing the same :peroentag'eofi wax?- mayx'diffet greatlyrin their sensitivitiesbe cause of diffierences' in .the method of application; It: therefore-,beoame highly desirable:- that there beravailable': a. procedurerforl the 1 detection of on coatedysensitiveispots andiuneven? distribution-of the: "wa- J!" in; the waxf -explosive mixture: Such a-gtechnique QWOilld theiusefulr inlthew, quality: control of explosive;propertieszin the manufac ture of phlegrnatized;explosivesuz This invention relates to a methodrandimeans for, estimating theecoating and. phlegmatizing ability of waxes asapplied to high explosives: It aims'in' particul'arto provide a means foresti' mating the sensitivit of high explosives which have been subject to such a phlegmatizing proc- 655. This invention is based upon our discovery that there is a definitemelations-hip between: the nonfluorescing areas of'a wax coated explosive composition and its sensitivity-. Ourresearches have shown thatjlight comihgtfromami'xture of: coatedi'and uncoatedi crystals, exposed to ultra: violet light ofcertain wavelengths,v varies fl'OllLBii deep purple: for-uncoated material to a brilliant: yellow: white or. bl'ue;white for coated material;

depending upon" the nature ofthe wax used; The hue of" the colon is definitely related to the sensitivity of the explosive. composition andthis is a result whichcouldlnothavesbeeni predicted in advance.

With the type of ultraviolet lamp and filter commonly used; which-produces alight having a maximum-'intensity'at 3660'angstr0m units, it hasbeenefound that there is no visible fluorescence ofhighly. nitrated highexplosives when exposed tor-thisdight'. (Dbservations under ultraviolet light aremadepinitheefollowing manner: (1') Hanov'ia analytic'model; (2) anA-G-E Mercury Arc, or" (3)? an Arclamp with iron electrod'es-in-conjunc-- tion with a #9863 Corning filter or'a triple filter consisti'ngaofthe-three following elements:- (a) 10% oopperls-ulfatesolution; 5mm: stratum; (lira #9863 Corning filter, and (c) a nitrosodimethyl aniline solution (10" :mgz per cc; H20), 5 mm. stratum. The fluorescing, sample is observed through eitheranEastman #ZA- filter or a double element filter consisting of' did'ymium' glass and K3glass; Withthisarrangementrefiectedultra violet light is cut oil from the eye' or the? camera. No special preparation of sample is necessary; Due to the passage "ofa small. amount of "visible violet and red lightthroughthe filters used with these lamps, nonfiuorescing specimens exposed to the light of the lamp takeona deep purple col'or. On the other hand, .waxes? exposedtothis light fluoresce with a brilliant yellow, blue or white light.

We have found that, as the-amountand uni; formit'y in distribution. of. the .wax increased, the color of""the sample rises from a deep purple, throughvarious shadesto abrilli'ant blue, white or 'yellowcolor." Samples may be screened'io'r observedwithout specialtreatment. The sample"; usually' about 1" gram; is" evenly distributed in asmall watch glass of 1 to 2 inches indiameter; However; even-afw uncoated crystals or even th'euncoated" face ofa' crystal may be readily detected by its purple color in the mass of brilliantly fluorescing material. The microscope is used when one seeks evidence of preferential adsorption of unevenness of wax distribution on tiny crystal faces. The desideratum, of course, is that there be no purple visible in the coated specimen. It may be emphasized, therefore, that our method does not depend upon any measurement of the color, hue or intensity of the fluorescent light but is concerned solely with the purple areas of uncoated material.

The method of application of the wax as illustrated by examples given below exerts a very large effect with regard to the uniformity of coating. So that with the same explosive composition, the same wax and the same percentage of wax it is possible by examination in ultraplosive, that is, in all examples pentaerythritol tetranitrate. I

1 Per Cent Degree of Impact Sens- Wax Coating 1 itivity 1 None 18-21 Albacer 9. 2 Poor 8. 0 do 29 8. 3 Fair 38 10.0 Very Good 74 9. 1 Fair 63 38.0 Poor. 23 Pentawax 286 10.0 do Pets 1 5.0 Good... 53 Pentawax 177 8.1 Excellent-.. 74 d0 13.1 do 100 1 This term is the opinion formed of the extent and homogeneity of the coating after inspection of the samples under ultra-violet light and with the aid of a microscope.

violet light to distinguish between samples as to 1 Abbreviation for pentaerythritol tetrastearate.

As has been pointed Tout heretofore, the uncoated face or faces of a crystal of explosive might be detected by the examination in ultra- Entirely dark-no observable coated areas. Unit of relative darkness-a few uncoatcd areas.

0 N 0 dark aressall exposed crystal faces coated.

r The figures in centimeters in the 5th column, represent the heights in centimeters from Which the 2 kilogram weight must be dropped in order to cause the explosive to detonate. Thus, not only does the examination in ultra-violet light furnish an indication as to the proper method of applying the wax but it also furnishes by visual examination an index as to the sensitivity of the coated product.

Examples of the preparation of wax coated explosive compositions are given as follows:

Example 1.SZurry process suspension of grams of pentaerythritol tetranitrate in 100 cc.-of water was heated to 90 C. while being stirred rapidly. The appropriate wax (8.8 grams suspended in 20 cc. of water at 90 C.) was then added over a 4-minute interval. The mixture was vigorously stirred while being cooled to 40 C. The waxed explosive was then filtered off and examined under ultra-violet light, no drying being necessary.

Example 2.C'oprecipitation process violet light. This technique was found to be important since in some cases where a desired reduction in sensitivity was not secured by the addition of a definite amount of wax present which was piled up on some crystal faceswhile others were left uncoated. The method of application was found to be at fault and by changing this a better coating was obtained. Since excessive amounts of wax or inert material may lower the brisance of the explosive composition, the determination of the presence of nonuniform coating by the wax through the technique of examination by ultra-violet light, eliminated the necessity of adding even larger amounts of Ibrisance lowering wax. In another instance in which a decrease in sensitivity did not accompany an increase in the percentage of wax added, examination of the coated material showed the presence of brilliantly fluorescing spherulites, scattered through the mass. Crushing of these spherulites showedthe absence of any crystals within themas well as did treatment with a solvent in which only the wax was soluble. Incompatibility was' found to be a large part of the trouble. The wax was found to have an electrical charge similar to that on the explosive; and the adhesive forceof wax was much stronger than that of wax to explosive. In consequence, spherulites of wax' were formed during the stirring of. wax and explosive. Neither chemical analysis nor microscopic examination in ordinary light were as effective as the ultra-violet light examination in revealing the source of the trouble.

We'claim: i I 1. In the art of phlegmatizin organic explosives, the method which comprises subjecting particles of such an explosive to treatment for the purpose of applying to them a coating of a phlegmatizing wax which exhibits fluorescence, after the said treatment exposing the so treated particles of explosive to ultraviolet light, and while the said so treated particles of explosive are being exposed to said ultraviolet light, examining the said so treated particles of explosive to determine the distribution of said wax with respect to said particles of explosive from the fluorescence exhibited by the said wax which became associated with said particles of explosive as a result of the said treatment.

2. In the art of estimating the distribution of a phlegmatizing fluorescent wax with respect to particles of an organic explosive which have been subjected to a treatment for the purpose of coatin them with said wax, the method which comprises exposing said so treated particles to ultraviolet light; and while said so treated particles are being exposed to said ultraviolet light, examining the said so treated particles to determine the distribution of said wax with respect to said particles from the fluorescence exhibited by the said wax that became associated with said particles as a result of the said treatment.

3. The method of estimating the phlegmatizing action of a fluorescent wax upon particles of an organic explosive or the effect upon its phlegmatizing action of the method used in applying the said wax to the particles of said explosive, the said method comprising subjecting the said particles of explosive to a treat ment for the purpose of applying a fluorescent phlegmatizing wax to the surface of said particles, after such treatment exposing at least a portion of the treated particles to ultraviolet light, and while the said so treated particles are being exposed to said ultraviolet light, ex-

U amining them to determine the extent of nonfluorescent area exhibited by them, whereby an estimate of the impact sensitivity of the said treated particles of explosive may be made.

4. The method of estimating the phlegmatizing action of a fluorescent wax upon particles of an organic explosive or the effect upon its phlegmatiZing action of the method used in applying the wax to the particles of said explosive, the said method comprising subjecting the said particles of explosive to a treatment for the purpose of applying a fluorescent phlegmatizing wax to the surface of said particles, after such treatment exposing at least a portion of the treated particles to ultraviolet light; and while the said so treated particles are being exposed to said ultraviolet light, photographing the said so treated particles through a filter which filters out ultraviolet light to obtain a record of the distribution of the fluorescence of the said wax that became associated with said particles of explosive as a result of said treatment.

JOHN W. BOWEN. T. DIXON DUDDERAR, Administrator of Estate of Albert J. Phillips,

deceased REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,355,269 Cairns Aug. 8, 1944 2,394,449 Herzog Feb. 5, 1946 OTHER REFERENCES Luminescence, Pringsheim et al., published by International Publishers, Inc., New York, N. Y., 1946 (pp. 118-124). 

1. IN THE ART OF PHLEGMATIZING ORGANIC EXPLOSIVES, THE METHOD WHICH COMPRISES SUBJECTING PARTICLES OF SUCH AN EXPLOSIVE TO TREATMENT FOR THE PURPOSE OF APPLYING TO THEM A COATING OF A PHLEGMATIZING WAX WHICH EXHIBITS FLUORESENCE, AFTER THE SAID TREATMENT EXPOSING THE SO TREATED PARTICLES OF EXPLOSIVE TO ULTRAVIOLET LIGHT, AND WHILE THE SAID SO TREATED PARTICLES OF EXPLOSIVE ARE BEING EXPOSED TO SAID ULTRAVIOLET LIGHT, EXPLOSIVE TO DETERMINE THE DISBRIBUTION OF SAID WAX WITH RESPECT TO SAID PARTICLES OF EXPLOSIVE FROM THE FLOURESCENCE EXHIBITED BY THE SAID WAX WHICH BECAME ASSOCIATED WITH SAID PARTICLES OF EXPLOSIVE AS A RESULT OF THE SAID TREATMENT. 